1. Field of the Invention
The present invention relates to an illumination apparatus and a projection display apparatus which separate a white light beam, emitted from a white light source, into a plurality of color component light beams, and modulate the plurality of color component light beams.
2. Description of the Related Art
A projection display apparatus currently known includes: a color separator configured to separate a white light beam, emitted from a white light source, into a plurality of color component light beams (a red component light beam R, a green component light beam G and a blue component light beam B); and a plurality of imagers each configured to modulate a corresponding one of the color component light beams.
A white light beam emitted from a white light source such as a UHP (Ultra-high Pressure) lamp includes a yellow component light beam Ye in addition to a red component light beam R, a green component light beam G, and a blue component light beam B. The yellow component light beam Ye has a wavelength band between those of the red component light beam R and the green component light beam G.
In general, the white light source of this kind outputs a relatively large quantity of light in the wavelength band of the yellow component light beam Ye. For this reason, active use of the yellow component light beam Ye has been attempted to increase the quantity of projected image light which is projected by a projection display apparatus. However, although the use of the yellow component light beam Ye increases the quantity of output light projected by the projection display apparatus, this use decreases color purities.
In this respect, examples of the projection display apparatus include a projection display apparatus used for a home theater and the like and a projection display apparatus used for outputting data and the like.
In the projection display apparatus used for the home theater, it is preferable that priority be given to purities of the respective colors rather than the quantity of output light. On the other hand, in the projection display apparatus used for outputting data, it is preferable that priority be given to the quantity of light rather than purities of the respective colors.
As described above, there is a need to switch a projection display apparatus between a mode in which priority is given to purities of the respective colors (hereinafter referred to as a “color-purity priority mode”) and a mode in which priority is given to the quantity of output light (hereinafter referred to as a “light-quantity priority mode”) depending on what the projection display apparatus is used for.
In response to this, a propose has been made for a projection display apparatus that uses a dichroic filter capable of removing a predetermined wavelength band (for example, the wavelength band of the yellow component light beam Ye) (see Japanese Patent Application Publication No. 2000-137289, for example).
Specifically, the dichroic filter is set in the optical path of a target color component light beam for the color-purity priority mode, whereas the dichroic filter is removed from the optical path of the target color component light beam for the light-quantity priority mode.
This mechanism makes it possible to switch a single projection display apparatus between the color-purity priority mode and the light-quantity priority mode.
However, the projection display apparatus of the foregoing type needs to move the dichroic filter mechanically. This makes it likely that the mechanism for moving the dichroic filter may break down.